An artistic impression of Diplomoceras Maximum
An ancient squid-like animal with a clam that looked like a five-foot-long paper clip has typically lived for 200 years.
Diplomoceras Maximum lived about 68 million years ago, making it a contemporary of Tyrannosaurus Rex. It was an ammonite – a now extinct group of tentacles of cephalopods – and had a characteristic paperclip-shaped shell.
“It’s hard not to be bewitched,” says Linda Ivany of Syracuse University in New York. “It’s as big as me.”
D. Maximum’s unusual bowl shape makes it difficult to unravel its biology, but Ivany and her colleague Emily Artruc have now uncovered evidence that individuals may have had very long lives. The evidence comes from chemical signatures trapped in samples taken at regular intervals along a 50 centimeter section of the D. Maximum dish.
When she and Artruc examined the carbon and oxygen isotopes along the shell, they found a repeating pattern in the isotope signatures that they suspect reflects the annual release of methane from the ocean floor. This annual pattern was consistent with the sculptural ridges or ribs perpendicular to the length of the bowl. This suggests that D. Maximum added a new rib to his shell every year. “These shells grow by accretion and add a new increment every year,” says Ivany.
Given that a 1.5 meter bowl contains many dozen of ribs, this leads to an obvious conclusion. “The only scenario that seems to work is to make this thing 200 years old,” says Ivany, who presented the research at an online meeting of the Geological Society of America last week.
At first glance, a 200 year old shellfish may seem inconspicuous, as some modern shellfish can live more than twice as long. But D. Maximum was a cephalopod, and all modern cephalopods live fast and die young. Octopuses and squids – even the gigantic shapes – don’t live more than 5 years. Nautilus, shelled cephalopods, can survive into their twenties. “These are not centenarians,” says Ivany.
Why D. Maximum may have had such a long lifespan is not clear. It lived in Antarctica, where it must have been difficult to get food in the long and dark winter. Ivany speculates that the ammonite may have had a slow metabolism and, as a side effect, lived a long life. Alternatively, long life could have been an adaptation to maximize the chances of successful reproduction in such a challenging environment.
In either case, the new length of life evidence will lead to a deeper understanding of the living paper clip lifestyle, Ivany says. “If you know anything about the lifespan of an organism, you learn a lot about its ecology.”
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